(218 days)
The SureWave Elastography device is intended for use with Siemens 1.5T and 3.0T MRI systems to generate shear wave vibrations in the body of adult patients during an MRI exam that are translated into images representing tissue stiffness. The images may be used for diagnostic purposes when interpreted by a trained physician.
The SureWave Elastography device is an accessory to the MRI system comprised of both hardware and software components. The hardware induces shear wave vibrations in the body through a transducer which is driven by a mobile tower and two flexible rotating axes. The transducer is fastened to the patient's body and contains a rotatable eccentric mass which induces vibrations in the body during an MRI scan. The SureWave Elastography reconstruction software uses the acquired image data from the MRI system to create images that show tissue stiffness.
The provided text describes the non-clinical and clinical tests performed to demonstrate the substantial equivalence of the SureWave Elastography device to its predicate devices. However, it does not explicitly define acceptance criteria in a table format with specific thresholds. It rather focuses on demonstrating similarity and accuracy to known values and predicate devices.
Based on the information provided, here's a structured response, with some sections noting what information is not present in the document.
1. A table of acceptance criteria and the reported device performance
The document does not explicitly state acceptance criteria in a quantitative table format with predefined thresholds. However, the study aims to demonstrate accuracy and repeatability comparable to, or better than, the predicate device and known phantom values. The reported performance is summarized below:
| Performance Metric | Implicit Acceptance Criteria (based on study design) | Reported Device Performance (SureWave 2D) | Reported Device Performance (SureWave 3D) | Notes/Comparison to Predicate |
|---|---|---|---|---|
| Accuracy (Phantom, kPa) | Values fall between predicate and expected values, and are comparable to expected values. | See table below. | See table below. | - SureWave Elastography 2D and 3D values fall between the predicate and expected stiffness values. |
- Computed stiffness values were "at least as accurate if not more accurate than the predicate method." |
| Specific Phantom Values: | | | | |
| Expected: 0.82 kPa | Close to 0.82 kPa | 0.76 ± 0.01 kPa (95% CI) | 0.73 ± 0.02 kPa (95% CI) |
| Expected: 2.02 kPa | Close to 2.02 kPa | 2.53 ± 0.94 kPa (95% CI) | 2.01 ± 0.07 kPa (95% CI) |
| Expected: 2.77 kPa | Close to 2.77 kPa | 3.83 ± 0.44 kPa (95% CI) | 3.27 ± 0.32 kPa (95% CI) |
| Expected: 5.80 kPa | Close to 5.80 kPa | 5.80 ± 0.67 kPa (95% CI) | 5.20 ± 0.09 kPa (95% CI) |
| Repeatability | Within 10% of the mean of the respective method, and comparable/better than predicate. | Within 10% of the mean. | Within 10% of the mean. | "Slightly better than that of the predicate." |
| Equivalency to Predicate (SureWave 2D) | Strong agreement with predicate, low bias. | Linear regression slope: 1.02 (R² = 0.99). Bland-Altman bias: 4%. | Not applicable. | "Excellent agreement," "no significant difference observed," "equivalent." |
| Equivalency to Predicate (SureWave 3D) | Strong linear relationship. Expected bias due to volumetric analysis. | Not applicable. | Linear regression R² = 0.99. Bland-Altman bias: approximately 20%. | "Strong linear relationship." Bias expected and potentially indicates more accuracy. |
2. Sample sizes used for the test set and the data provenance
- Accuracy Test (Phantom):
- Sample Size: Not explicitly stated as a "sample size" for a test set, but referred to as "MRE acquisitions from SureWave Elastography 2D, SureWave Elastography 3D, and the predicate MRE methods." The number of acquisitions per method for the general QA phantom repeatability testing was 240 measurements. It is implied similar extensive measurements were taken for the multi-component QA phantom.
- Data Provenance: Not explicitly stated (e.g., country of origin, retrospective/prospective clinical data). The phantom study is a bench test, not human data.
- Equivalency Test (Volunteer):
- Sample Size: 22 healthy adult volunteers.
- Data Provenance: Not explicitly stated (e.g., country of origin). The study involved "healthy adult volunteers," implying a prospective human study.
3. Number of experts used to establish the ground truth for the test set and the qualifications of those experts
- Phantom Studies: Ground truth for the phantom was established by the phantom manufacturer ("expected stiffness values established by the phantom manufacturer"). No human experts were involved in establishing this ground truth.
- Volunteer Studies: For the healthy volunteer equivalency study, the "ground truth" was effectively established by the predicate device's measurements. The document states that the SureWave Elastography measurements were plotted against the predicate device to assess their relationship and bias. No independent expert consensus or interpretation was described as establishing a separate ground truth for this human volunteer data beyond the predicate device as the comparison standard.
4. Adjudication method (e.g. 2+1, 3+1, none) for the test set
- No adjudication method (e.g., expert consensus or multi-reader review beyond the device's output) is described for either the phantom or volunteer test sets. The focus appears to be on direct numerical comparison of the device's output against known phantom values or predicate device measurements.
5. If a multi-reader multi-case (MRMC) comparative effectiveness study was done, If so, what was the effect size of how much human readers improve with AI vs without AI assistance
- No MRMC comparative effectiveness study involving human readers and AI assistance is described. The study focuses on the device's performance in terms of stiffness measurement accuracy and repeatability, and its equivalence to a predicate device, not on diagnostic improvement for human readers. The device outputs images that are "interpreted by a trained physician," but the study does not evaluate this physician interpretation process.
6. If a standalone (i.e. algorithm only without human-in-the-loop performance) was done
- Yes, the conducted tests, precisely the phantom and volunteer studies, evaluate the standalone performance of the SureWave Elastography device in generating stiffness measurements. The device produces quantitative stiffness values (kPa) and qualitative stiffness maps, confidence overlays, and wave images. The accuracy and repeatability of these outputs were directly assessed. While a trained physician interprets the images, the study's focus is on the device's ability to accurately produce those measurements, independent of a specific physician's interpretation improvement.
7. The type of ground truth used (expert consensus, pathology, outcomes data, etc)
- Phantom Studies: The ground truth was known physical properties of the phantom components, as provided by the phantom manufacturer.
- Volunteer Studies: The ground truth for comparison was the measurements obtained from the legally marketed predicate device.
8. The sample size for the training set
- The document does not provide information about a training set size. The described tests relate to the validation or verification of the device's performance, implying it has already been developed. As this is a 510(k) submission for a device that generates physical properties (stiffness) rather than AI-based diagnostic interpretations, it's possible a separate "training set" in the machine learning sense was not explicitly required or detailed in this summary.
9. How the ground truth for the training set was established
- As no training set is described, information on how its ground truth was established is also not present in the document.
§ 892.1000 Magnetic resonance diagnostic device.
(a)
Identification. A magnetic resonance diagnostic device is intended for general diagnostic use to present images which reflect the spatial distribution and/or magnetic resonance spectra which reflect frequency and distribution of nuclei exhibiting nuclear magnetic resonance. Other physical parameters derived from the images and/or spectra may also be produced. The device includes hydrogen-1 (proton) imaging, sodium-23 imaging, hydrogen-1 spectroscopy, phosphorus-31 spectroscopy, and chemical shift imaging (preserving simultaneous frequency and spatial information).(b)
Classification. Class II (special controls). A magnetic resonance imaging disposable kit intended for use with a magnetic resonance diagnostic device only is exempt from the premarket notification procedures in subpart E of part 807 of this chapter subject to the limitations in § 892.9.